William ate 2 slices of pie. Nadia ate 5 slices. If William ate $\dfrac{2}{10}$ of the pie, what fraction of the pie is remaining?
Solution: If 2 slices represent $\dfrac{2}{10}$ of the pie, there must have been a total of 10 slices. $\text{fraction of pie remaining} = \dfrac{\text{number of slices remaining}}{\text{number of slices total}}$ Together they ate 7 slices, which leaves 3 out of 10 slices remaining. There is $\dfrac{3}{10}$ of the pie remaining.